DE69709325T2 - ROTARY ACTUATOR AND STEERING GEARBOX FOR A VALVE - Google Patents

Description

The present invention relates generally to a rotary valve actuator and a linkage for an actuator, and more particularly to a simplified actuator assembly that can be manufactured at lower cost and requires less space.

When using rotary operated valves such as rotary plug valves and butterfly valves, it is common to use an actuator that converts linear actuator motion into rotary motion. This rotary motion serves to open and close the valve spool or plug. One such rotary valve is shown and described in Baumann, U.S. Patent No. 5,305,987. In that document, a linkage is provided at the end of the shaft. This linkage is connected to a linear actuator device. Such actuators often have large mechanical housings that receive air and cause translational motion of the linear actuator component by interaction with a rolling diaphragm that moves in response to applied pressure. The housing is supported relative to the valve body by a large frame that provides space for the movement of the required linkages.

The approach outlined above for constructing a rotary valve unit, while effective, requires a relatively large amount of space around the valve body itself for the actuator assembly. Likewise, the actuator assembly is relatively complex and therefore expensive to construct and maintain. Maintenance itself is difficult because the body must be assembled and disassembled under the pressure of a long compression spring. Assembly and disassembly require the respective installation and removal of several threaded bolts and other components.

It has also been recognized that the rods that convert linear translational motion into rotary motion of the shaft often have backlash and/or are difficult to attach to a shaft. Many rotary valve shafts define a square cross-section, which can create backlash if the rod is not precisely sized to match the shaft. A splined shaft would reduce backlash but would make rod misalignment more likely since the rod can be positioned in a large number of rotational orientations. However, a square cross-section is more likely to allow play between the rod and the shaft as the rod is rotated to rotate the shaft. The use of set screws or complicated clamping devices to increase the strength between the rod and the shaft has been suggested, but these designs increase the complexity of the connection between the components and therefore the cost in terms of assembly time for a valve. U.S. Patent No. 4,345,850 to Baumann shows a new rotary valve rod assembly in which movements are created in each of two opposing arms, thereby "clamping" the two arms into tight engagement with the square shaft end. The use of this rod assembly is limited to cases where the two arms are in relatively close proximity to each other, since the arms must abut each other to create the required moment for secure engagement. It is thus desirable to provide a rod assembly that will tightly engage a square cross-section shaft while allowing greater spacing between arm sections.

It is therefore an object of the present invention to provide a rotary valve actuator assembly which is reliable, easy to maintain and takes up less space than a more conventional actuator. This actuator should be usable with many different types of rotary valves and permit rotary motion in each of opposite directions with relative accuracy. The actuator should produce sufficient rotary force to operate most small to medium sized valves. A linkage which may be used in conjunction with this actuator should permit tight engagement with a square or other shaped shaft when two or more arms of the linkage are provided at a predetermined distance from each other.

GB-A-1240746 describes a method of manufacturing a valve actuator and in particular comprises the steps of: casting first and second housing halves which are substantially identical; individually finishing first and predetermined regions of each half; assembling the halves together and finishing second predetermined regions of each half to thereby form continuous bearing surfaces at opposing non-contacting regions of the halves.

The present invention overcomes the disadvantages of the prior art by providing a rotary valve actuator assembly according to claims 1 to 26. The rotary valve actuator assembly has a housing and a piston mounted in the housing and movable relative to the housing along an elongated housing axis, a fluid pressure source coupled to the housing for moving the piston along the axis. The housing is a tubular housing and has a pair of openings on opposite sides thereof, and the linkage has two arms which engage the pistons through the openings in the tubular housing. The linkage is connected to a rotatable shaft which is completely outside the tubular housing, whereby the movement of the piston along the axis causes the linkage to rotate the shaft.

The foregoing and other objects and advantages of the invention will become apparent by reference to the following detailed description of the preferred embodiments as illustrated in the drawings, in which:

Fig. 1 is a perspective view of a rotary valve and actuator assembly according to the present invention;

Fig. 2 is a partial open perspective view of the actuator assembly of Fig. 1;

Fig. 3 is an open perspective view of the actuator assembly with the orientation of the actuator reversed ;

Fig. 4 is a side cross-sectional view of the actuator assembly taken along line 4-4 of Fig. 2;

Fig. 5 is another cross-section through the actuator assembly showing the relative positions of the actuator piston and linkage;

Fig. 6 is a front cross-section of the actuator assembly taken along line 6-6 of Fig. 5;

Fig. 7 is a partial cross-sectional view of the linkage for use with the actuator assembly according to the present invention;

Fig. 8A, 8B and 8C are partial cross-sections of shafts and mating rods taken along line 8-8 of Fig. 7; and

Figure 9 is a somewhat schematic exploded view of a rod and wedge system for use with a square cross-section shaft in accordance with the present invention.

Fig. 1 shows in overview a rotary valve and actuator assembly according to the present invention. The valve housing 20 can comprise any type of rotary operated valve in which a plug or slide member (not shown) regulates the flow between an inlet 22 and an outlet 24 based on the rotational movement of the slide. The valve 20 is connected to the actuator assembly 28 of the present invention via a flange assembly 26. The actuator assembly comprises a housing 30 having a front half 32 and a rear half 34. The rear half engages the flange assembly 26. The housing 30 can be made of any suitable material such as cast aluminum, iron or stainless steel. It may be formed using a casting or stamping process if a relatively close fit of the front and rear halves 32 and 34 is desired; this area of the housing is not typically airtight and therefore many different inexpensive manufacturing processes may be used.

A manual override/end stop screw 36 and a hand wheel 38 are provided. The screw 36 can be received in either of two threaded bases 40 and 42 on the rear portion of the housing. The function of the screw 36 is described below. In this embodiment, the front and rear halves 32 and 34 are connected together by a series of flanges 44 which receive threaded bolts. The two halves 32 and 34 secure between them the actuator element 48 according to the invention. The actuator element 48 is formed as an integral unit and in this embodiment receives fluid pressure through a fitting 50 which is connected to a pressure line 52.

Fluid pressure in the form of air, other gas or liquid is used to control the movement of the actuator member 48 in accordance with the present invention.

The relative movement of the actuator in this embodiment is indicated by a scale 54 and a moving pointer 56 (Fig. 1) mounted on one end of the actuator rod assembly shown in detail in Figs. 2 et seq. Referring to Figs. 2 through 5, the front half of the housing has been removed to show the internal operation of the actuator assembly. The actuator member 48 in this embodiment is made of a seamless tube made of a durable material such as stainless steel. In this embodiment, readily available tubing can be used to reduce cost and manufacturing time associated with the actuator member 48. The actuator member 48 includes a pair of opposed machined openings 60 which expose the interior of the tube. The linkage 62 is operatively connected to the actuator element 48 through the openings 60.

Referring to Figures 4 to 6, the linkage includes two arms 64 and 66 which are fixedly secured to a square cross-section shaft 68. The end 70 of the shaft 68 may be threaded (see Figure 3) to receive a lock nut 72 as seen in Figure 1. The mechanism for securing the arms 64 and 66 to the shaft 68 is described below.

Each arm 64, 66 has an associated guide block 74, 76, respectively. The guide blocks are received in corresponding slots 80 formed in the side walls of the actuator piston 82 of the invention. As shown in detail in Fig. 5, forward and backward movement (double arrow 84) of the piston 82 within the actuator tube causes a corresponding rotational movement (curved arrows 86) of the linkage 62. The blocks 74 and 76 move along the respective slots 80 as the linkage 62 rotates (see double arrows 88A in Fig. 5). Therefore, the slots accommodate a change in position of the arm in a direction transverse to the central axis of the cylindrical tube. The blocks 74 and 76 pivot relative to their respective arms 64 and 66 to facilitate movement along the slots 80. The pivoting movement is accomplished using screws 88 which are freely pivotable relative to the arm ends 90 and 92 (Fig. 6). The piston in this embodiment is molded from a sturdy plastic such as nylon or Delrin®. These materials are self-lubricating and therefore only minimal lubrication of the piston relative to the tube is required. The piston 82 has a hollow center which is open at the front 96 to accommodate a spring 98. The spring bears against the rear wall 100 of the piston and a stationary front wall 102 of the tube. The spring constant and the applied force of the spring relative to the piston are selected so that when the maximum pressure is applied to the actuator, the spring force is overcome and the piston is moved to a fully forward position (103 in Fig. 5). In this embodiment, a maximum pressure of about 6.895 x 10⁵ N/m² (100 psi) is provided which produces a maximum force of about 226.80 kg (500 pounds) within the piston and a torque of about 3.103 x 10⁵ N/m² (450 inch pounds). These values can be changed depending on the size and function of the actuator assembly according to the present invention.

The piston 82 of the present embodiment has a main wall portion 106 spaced from the inner wall of the tube. Two sets of guide rings 108 and 110 engage the inner wall of the tube. By minimizing surface contact between the piston 82 and the inner wall of the tube, friction is reduced and the risk of Binding between the components is minimized. The rear ring 108 has a diameter approximately 1/16 smaller than the inner diameter of the tube. The outer ring 110 is more closely matched to the diameter of the inner diameter of the tube. The opening 60 makes the tube more likely to deform and therefore the more closely matched front ring assembly 110 provides additional support to the tube at its weakest point.

As mentioned above, the tube of actuator member 48 is made of seamless stainless steel tubing. In the valve shown, the diameter of the tube is approximately 4 inches. The wall thickness is approximately 1/16 inch. The front end cap 102 is removable so that the interior of member 48 can be serviced. A snap ring 120 is seated in a recess 122 formed in the interior of the tube. The recess is of sufficient depth to prevent the snap ring from moving axially out of the tube opening. The end cap 102, which is made of stainless steel or a similar durable material, has a shoulder 124 which abuts the snap ring. As shown in detail in Figs. 2 and 3, a plastic cap 126 may be disposed in a hole in the end cap. However, this hole and cap 126 may be omitted. The end cap 102 is installed and removed by biasing the cap inwardly against the spring 98 until it has passed the snap ring 120. After the end cap 102 has passed the snap ring 120, it can be removed or installed relative to the recess 124. Large diameter snap rings as shown are available from various industrial manufacturers in Germany and elsewhere. Under spring loading, it is impossible to loosen the snap ring 120 because the circumferential shoulder 125 of the cap 102 is in tight engagement with the inner diameter of the snap ring, thus locking the snap ring thereto. from moving radially inward out of the groove 122.

The actuator member 48 further includes an opposing base cap 130 which is cast or molded into a domed shape. This domed shape helps maintain high pressure. An opening 132 places the fluid line 52 in communication with the interior of the actuator member in the region of the end cap 130. The end cap 130 is permanently secured to the tube by a plastically deformed end wall 134 formed in the rear end of the tube. The deformed end wall prevents the end cap 130 from moving axially outwardly away from the tube. Suitable welds or solder joints may also be provided between the tube and the end cap. It is generally contemplated that the end cap 130 will be press-fitted. The end cap 130 includes a generally cylindrical inner portion 136 which engages the inner wall of the tube. The inner wall portion 136 includes a recess 138 for receiving the base 140 which also serves as a radial static seal of a rolling diaphragm 142. The rolling diaphragm is available from a variety of industrial sources. In this embodiment, it is a nitrile rubber reinforced fabric having a thickness of approximately 0.00106 m (0.04 inch). The rolling diaphragm occupies the space between the main wall 106 of the piston 82 and the inner wall of the tube at the rear of the ring 108. As shown in Figure 5, pressure causes the diaphragm to abut the rear wall 100 of the piston 82, thereby moving the piston forward toward the front end cap 102. The diaphragm forms a positive fluid seal within the rear region of the actuator member 48. Thus, the actuator and piston assembly is open and unsealed forward of the diaphragm 142. From this description it is apparent that the actuator element 48 shown and described is relatively easy to build and maintain and occupies less space than conventional actuators. It is constructed essentially without screws or other fasteners and, if damaged, can be considered disposable. However, servicing of the actuator is possible through the removable front cap 102, as stated above. In addition to the advantages described above, Figs. 2 and 3 show the added versatility of the actuator assembly according to the present invention. The recess 122 adjacent the front cap 102 serves as a retaining ring which seats in corresponding recesses 148 in the rear housing half 34 (Fig. 2). The actuator element 48 is symmetrically designed so that it can be rotated 180° and inserted into an opposing set of recesses 150 in the rear housing half 34 (Fig. 3). Thus, by a simple rearrangement operation, the actuator element 48 can be positioned to operate in either of opposite directions relative to the valve. In the present embodiment, the set of recesses not in use (e.g., the recesses not engaged with the front cap assembly) may be filled with an O-ring of appropriate size and thickness to further securely mount the central portion of the actuator member 48.

The upper portion of the rod 62 includes a stop structure 150 which rotates together with the arms 64 and 65 (Fig. 5). The stop structure includes a roller 152 which reduces friction when engaging the threaded stops disposed in the bases 40 and 42. As described above, the screw 36 and an opposing screw (156 in Fig. 5) can, if desired, be moved relative to their respective bases 40 and 42 to define the end stop positions of the rod 62. Otherwise, the end stop positions are defined by the minimum and maximum movement of the piston 82 within of the tube of the actuator member 48. The screw 36 can also be used for manual override in the event of a pressure failure. When the screw is turned inward, it causes the stop structure 150A to rotate the shaft 68, thereby moving the valve spool (not shown). The movement of the stop structure 150 overcomes the force applied by the spring 98.

With further reference to Figures 7-9, the mounting mechanism for a linkage 62 according to the present invention is shown and described. In particular, Figure 7 shows the mounting of the linkage 62 on a square cross-section shaft 68 connected to the valve body of a rotary valve (not shown). In this embodiment, the square cross-section portion of the shaft 68 is formed from a larger diameter round shaft, the round portion 160 of the shaft defining a shoulder 162 against which an inner end of the arm 64 abuts. The free end of the shaft 68 in this embodiment is rounded and provided with an end portion 70 which is threaded for receiving a nut 72. The length of the shaft portion with square cross-section is selected so that the nut 72 can be fully tightened to apply a force (arrow 164) to the rod assembly 62.

In this embodiment, the stop portion 150 defines a center portion of the linkage 62. It includes a square cross-section hole that is relatively closely matched to the size and shape of the square cross-section shaft 68. In this embodiment, opposing upper legs of the stop structure 150 define splines 166 that extend away from the stop structure in opposite directions. In particular, the splines 166 define extensions that extend beyond the end walls 168 of the lower portion 170 of the stop structure 150. Referring to 8A and 9, each arm 64 and 66 includes a respective mounting base or arm end 174 and 176 also formed with a square cross-section hole. These holes are adapted to the size and shape of the shaft 68. Each arm end 174 and 176 further includes an inwardly facing triangular recess 180 sized and arranged to receive a respective wedge 166. The angle of the wedge may be approximately 15º or more or less. This angle may be variable depending on the application. Referring again to Fig. 7, by applying force (arrow 164) to the linkage 62, the opposing arm ends 174 and 176 are pressed in compression (arrows 184 and 186, respectively) against the wedges 166 of the stop structure 150. Because the keys and mating slots in the arm ends 174 and 176 are angled, they break down the compression force (arrows 184 and 186) into vertical force components (arrows 194, 196 and 198) which drive the arm ends 174 and 176 and the stop structure 150 into tight engagement with the flats of the shaft 68. The tighter the nut 72 is turned on the shaft end 70, the tighter the engagement of the linkage components with the flats of the shaft 68. As long as the walls of the shaft ends 174 and 176 are sufficiently robust, a very considerable locking force can be applied to the linkage components. This locking force greatly reduces the possibility of backlash when the arms 64 and 66 are operated to rotate the shaft 68.

It should be noted that, as shown in Fig. 7, a gap 200 should be provided between the end walls 168 of the stop structure and the corresponding end walls 202 of each arm end 174 and 176. Without this gap, the components may not have sufficient room to move vertically into a fully engaged position with the flats of the shaft 68.

It will be appreciated that the basic principle described here is applicable to a variety of shaft shapes. It is generally advantageous if the shaft has at least one flat. For example, Figures 8B and 8C show shafts 268 and 368 which are round and hexagonal, respectively. Each shaft 268 and 368 has at least one flat 290 and 390 on which a key 266 and 366 can sit in abutment. The respective arm end 274 and 374 has a hole adapted to the shape of the shaft with a suitably angled cutout 280 or 380 for receiving the key 266 or 366. Likewise, the central area carrying the key need not have a surrounding housing with a hole for receiving the shaft. Instead, as shown in Figure 9, the center piece may comprise a single one-piece plate 208 with keys 166 defined at each end. The length of the plate 208 or other key-bearing structure is infinitely variable and thus the arms may be spaced a considerable distance apart in accordance with the present invention. Furthermore, while the shaft has an abutment wall 162, nuts or other fastening structures may be provided at both ends and adjusted so that the compressive force and position of the linkage can be changed as required.

It will be appreciated that the arm attachment mechanism described here allows arms and shafts to be manufactured to a somewhat tighter tolerance and yet provide a relatively backlash-free fit. Arms may be manufactured using casting or other molding techniques in accordance with this embodiment.

The foregoing is a detailed description of a preferred embodiment. Various modifications and equivalents are possible without departing from the scope of the invention. For example, although in this embodiment a rolling diaphragm but a hermetic piston may be used instead if desired. The size and shape of the components may be changed for use with different types of rotary valves and the actuator assembly described herein may be used with or without the special linkage attachment shown and described. Likewise, the linkage attachment may be applied to other designs where it is desirable to attach arms to shafts using a quick and inexpensive technique. Therefore, the present description is exemplary only and does not limit the scope of the invention.

Claims (26)

1. A rotary valve actuator assembly (30) comprising: a housing and a piston (82) mounted in the housing and movable relative to the housing along an elongated housing axis, a fluid pressure source (52) coupled to the housing for moving the piston (82) along the axis; the housing being a tubular housing (48) and a linkage (62) having two arms (64, 66) interconnecting the piston and the rotatable shaft, characterized in that the housing has a pair of openings (60) on opposite sides thereof; and the linkage (62) engages the piston through the openings in the tubular housing, the linkage (62) being located entirely outside the tubular housing (48), and movement of the piston (82) along the axis causes the linkage (62) to rotate the shaft (68). 2. The rotary valve actuator assembly of claim 1, further comprising a linkage housing (32, 34) receiving the tubular housing (48) and holding the tubular housing (48) stationary relative to the shaft. 3. Rotary valve actuator assembly according to claim 2, wherein the tubular housing (48) has a rolling diaphragm (142) which is connected between a closed end (130) the tubular housing (48) and the piston (82). 4. A rotary valve actuator assembly as claimed in claim 3, further comprising a compression spring (98) disposed between an end (102) of the tubular housing (48) and a portion (100) of the piston (82) remote from the rolling diaphragm (142) for biasing the piston (82) in a predetermined direction which is overcome by the application of fluid pressure. 5. A rotary valve actuator assembly according to claim 4, wherein the arms (64, 66) have hinge blocks (74, 76) that slide along slots (80) formed in the piston (82). 6. A rotary valve actuator assembly as claimed in claim 5, wherein the shaft (68) has at least one flat surface thereon and wherein the arms have arm ends, each of which has matching flats that engage the flat on the shaft (68). 7. Rotary valve actuator assembly according to claim 6, wherein the shaft (68) comprises a square cross-section shaft (68) having four flats. 8. Rotary valve actuator assembly according to claim 7, further comprising a stop structure (150) disposed between each of the arms and extending in a direction opposite to an extension direction of the arms, and further comprising at least one adjustable stop (38) constructed and arranged to engage the stop structure at predetermined variable locations to limit rotation of the shaft (68). 9. Rotary valve actuator assembly according to claim 8, wherein the stop structure (150) comprises a roller (152) that engages the adjustable stop (40, 42). 10. The rotary valve actuator assembly of claim 9, wherein the adjustable stop (40, 42) includes a screw (36) and wherein the linkage housing includes a threaded base (40, 42) that receives the screw (36). 11. A rotary valve actuator assembly as claimed in claim 10, wherein each of the arm ends includes an angled slot and wherein the stop structure includes two opposing wedges (166) and wherein the slot and the wedges are constructed and arranged to engage one another so that each of the arm ends and the stop structure bears against the shaft in axial compression. 12. Rotary valve actuator assembly according to claim 1, wherein the piston (82) comprises a synthetic material. 13. Rotary valve actuator assembly according to claim 12, wherein the piston (82) has guide rings (108, 110) having diameters approximately equal to the diameter of an inner wall of the tubular housing (48), and wherein the piston (82) has a main wall (106) remote from the inner wall of the tubular housing (48). 14. The rotary valve actuator assembly of claim 1, wherein the tubular housing (48) comprises a seamless stainless steel tube. 15. The rotary valve actuator assembly of claim 14, wherein the tubular housing (48) includes a removable end cap (102) secured by a snap ring (120) in the tubular housing (48). 16. Rotary valve actuator assembly according to claim 15, further comprising a recess (122) for receiving the snap ring formed in an inner wall of the tubular housing (48). 17. The rotary valve actuator assembly of claim 16, further comprising a linkage housing (34) for supporting the tubular housing (48), the linkage housing having a recess (148) for receiving a protrusion formed in an outer wall of the recess (148) for receiving the snap ring (120). 18. The rotary valve actuator assembly of claim 17, wherein the linkage housing has two pairs of recesses (150), each of which receives the projection of the tubular housing (48) in each of opposite orientations of the tubular housing (48) relative to the linkage housing. 19. Rotary valve actuator assembly according to claim 1, wherein the linkage for a rotatable shaft comprises: a shaft arranged to be rotatable, the shaft (68) having at least one flat surface extending along a portion thereof, the shaft (68) having an elongated axis; an abutment (162) arranged along the shaft (68); two arms having arm ends, the arm ends (174, 176) having holes sized and arranged to pass over the portion of the shaft (68) having the flat surface, each of the holes having an angled recess (180); a wedge structure (166) having a predetermined length and two wedge surfaces sized and arranged to engage the angled recess (180) in each of the arm ends; and an adjustable end stop (150) applying a force to each of the arm ends and the wedge structure in the direction of the axis, at least one of the arm ends abutting the stop (162) so that each of the arm ends is forced into engagement with the shaft (68) and the wedge structure is forced into engagement with the flat surface. 20. A rotary valve actuator assembly as claimed in claim 19, wherein the key structure comprises a body having a hole sized and arranged to pass over the portion of the shaft (68) having a flat surface, and the body having end edges over at least a portion thereof. 21. A rotary valve actuator assembly as claimed in claim 20, wherein the wedge surfaces extend outwardly from the end edges. 22. A rotary valve actuator assembly as claimed in claim 21, wherein the wedge surfaces are sized and arranged to extend along and into engagement with the flat surface. 23. A rotary valve actuator assembly according to claim 19, wherein the shaft (68) comprises a shaft having a square cross-section. 24. The rotary valve actuator assembly of claim 19, wherein the shaft (68) comprises a shaft (268) having a round cross-section at a portion thereof. 25. The rotary valve actuator assembly of claim 19, wherein the shaft (68) comprises a shaft (368) having a hexagonal cross-section. 26. A rotary valve actuator assembly according to claim 19, wherein the wedge structure has a stop structure (150) extending therefrom, dimensioned and arranged to engage with at least one stop when the shaft rotates to a predetermined angular position.